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Immune system police are as good at recognizing bad guys, such as bacteria and viruses, as they are our own tissue, researchers say.

The finding may cause a stir in the scientific community, which has long held that regulatory T cells or Tregs, preferentially respond to body proteins, or self antigens, rather than non-self antigens, invaders such as viruses and bacteria.

Now, Medical College of Georgia immunologists report in the September issue of Immunity that Tregs, similarly to other T cells, respond stronger and more frequently to foreign substances than to the bodys own antigens.

Fortunately, the potential conflict between nave and regulatory T cells, in which the former lead the attack against invaders and the latter try to protect invaders, usually doesnt exist, the scientists say.

That?s probably because other types of immune cells come to help T cells fight an infection, says Dr. Rafal Pacholczyk, a corresponding author for the study.

During the normal immune response, Tregs sit in the back seat and, in most cases, dont interfere, says Dr. Leszek Ignatowicz, also a corresponding author.

Still, emerging therapies to fight autoimmune diseases, such as arthritis, multiple sclerosis and type 1 diabetes, by boosting the total number of Tregs could unintentionally upset the balance between nave T cells and Tregs, they say.

Regulatory cells always suppress immunity, whether it?s to a virus, bacteria or our own tissue, says Dr. Ignatowicz.

We have to be really careful with manipulating regulatory T cells as a whole, adds Dr. Pacholczyk. If we want to promote more regulatory cells in the body, we have to find a way to promote only those in which specificities are known.

Oral insulin, which appears to boost the number of Tregs that recognize and protect insulin-producing pancreatic cells from the immune system, is a good example of how this targeted promotion may work for type
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